In contrast to a threadless ball screw, the balls in a ball screw nut may not circulate or deflect. The balls may move in both directions until they reach a stop.
Such ball screws may be used as components of an electromechanical actuator. An electric drive motor is coupled thereby with either the spindle or the ball screw nut, such that the rotational movement generated by the drive motor is converted to a linear movement. An electromechanical actuator of this type can be used as a brake or as a parking brake in a motor vehicle, in that a displacement of the ball screw nut displaces a piston of a hydraulic brake system, in a manner of which brake pads are pressed against the brake disk.
A ball screw is known from WO 2009/053359 A1, in which springs are located in the tracks, in addition to balls. As a result, the availability of a roller path in which the balls can roll is always ensured. The balls roll when subjected to a load, but they can be displaced when they are actuated without a load. Because numerous spring elements, referred to therein as intermediate spring elements, are used, the friction may be reduced between adjacent balls.
A ball screw drive, as shown in DE 10 2013 202 099 A1 discloses a rod disposed between its race and its spring element.
Another ball screw drive is proposed in DE 10 2009 012 235 A1, which also includes a roller bearing race. The race prevents the rollers from touching one another, and as a result, a reduction in the efficiency caused by friction is prevented. Because a spring element bears on the race, an end of the spring element can be displaced under load between the race and the tracks or the grooves of the spindle or the ball screw nut, resulting in an unintended change in the spring force.
The embodiments therefore may address the object of creating a ball screw that is designed such that the end section of a spring element cannot become jammed.
In order to achieve this objective, a ball drive is disclosed that includes a ball that is disposed between the race and the at least one spring element.